This invention relates to a device for generating video signals from binary information, and more particularly to a device for providing symbol information stored in digital form for use on a display medium.
A fundamental operation in display systems is the conversion of data from its original form into information that is compatible with visual presentation. The input data may either be digital or analog, which may also include data entered into the system by means of an input device such as a light pen. The total process is generally designated by the general term data conversion. The output information from digital computers, for example, is often stored in a memory device and read out from such a device onto a cathode ray tube display. Prior art cathode ray tube display devices for this purpose are generally specially constructed units utilizing relatively slow speed scanning in which the scanning beam is deflected or bent to form the symbols to be displayed in accordance with the memory output. The output information of a computer as handled in the prior art for video display, however, is not suitable for display on the screen of an ordinary television receiver in view of the relatively high-speed linear scan utilized in television apparatus.
A device taught by Johnson in U.S. Pat. No. 3,528,068 provides means for processing the output of the digital computer so that it is converted to a form suitable for display on the screen of an ordinary television receiver. His device accomplishes this result by first storing the symbol information to be displayed in a high-speed random access memory, with the information being in binary coded form. The binary coded information is read sequentially out of the memory into a symbol generator where it is translated into a series of linear dot patterns. A predetermined number of lines of such dot patterns represent the symbols to be displayed. The symbol generator is synchronized with the television cathode ray tube scan so that the dot pattern output which is fed to the video circuits of the receiver appear on the cathode ray tube in appropriate positions on the scanning raster. The symbol generator forms the dot patterns of each line of the symbols in a row in sequence, appropriate gating circuitry being utilized in conjunction with the magnetic read-out core to display the proper dot patterns at the appropriate times.
U.S. Pat application Ser. No. 418,509 filed Nov. 23, 1973, and assigned to the assignee of the present invention, teaches an organization of random access memories and control elements which provide for a high-resolution display and a combination of features such as variable line width, proportional space characters, and seqmented display rasters not taught by the prior art.
It is an object of the present invention to provide additional features which advance the state of display technology.
It is another object of the present invention to provide an intermediate storage of the information bit pattern prior to character generation.
It is still another object of the present invention to optimize the use of the bit pattern store by means of a font definition matrix for each character along with provision for the vertical off-setting of font characters to be displayed.
It is yet another feature of the present invention to provide the generation of high quality video information for display.
Other objects of the invention will be evident from the description hereinafter presented.